Blend of isoolefin-diolefin and polychloroprene synthetic rubbers for adhering isoolefin-diolefin rubber to other materials



Feb- 13, 1951 D. v. sARBAcH ET AL 2,541,550

BLEND oF IsooLEFTN-DTOLEFTN AND PoLYcHLoRoPRENE SYNTHETIC RUBEERS RoR ADHERTNG IsooLEEIN-DIOLERTN RUBBER To OTHER MATERIALS Filed Jan. 3, 1949 Patented Feb.-` 13, 19,51-

'I UNITED STATES 'I PATENT OFFICE BLEND F ISOOLEFlN-DIOLEFIN AND POLY- CHLOROPBENE SYNTHETIC RUBBERS FOR ADHERING ISOOLEFIN-DIOLEFIN RUBBER T0 OTHER MATERIALS Application January 3, 1949, Serial No. 68,824

11 claims. l

This invention relates to adhesive compositions for adhering rubbery compositions to each other or to iilamentary materials and to methods of using such adhesives in the building of composite articles of rubbery materials, such as tires and the like.

' It is an object of this invention to provide liquid or solid adhesive compositions which may be used for adhering rubbery materials.

It is a further object to provide an adhesive for adhering isoolen-diolen copolymer synthetic rubber to other rubbery materials or to illamentary materials. It is also an object to provide an adhesive fo treating a illamentary material which may be used as an interposed layer between layers of rubbery materials which are to be adhered together, and especially between a layer of isooleiindiolen copolymer synthetic rubber and a layer of any other rubbery material.

Other objects will be apparent .from the description which follows. l

These objects are attained by preparing an adhesive comprising a homogeneous blend of two or more rubbery materials and preferably a blend of isoolenediolelln copolymer lsynthetic rubber with neoprene.

reinforcing ingredients to form a solid adhesive composition which may be used in that condition or may be dissolved in a suitable solvent to form a liquid cement.- By interposing such an adhesive composition between an isoolefln-diolen copolymer synthetic rubber and another rubbery material or a lamentary material, then vulcanizing the composite product, a `good bond is achieved between the materials.

'The isoolefm-dlolefln copolymer synthetic-ruby bers included in this invention areknown as Butyl rubber and are rubbery hydrocarbon copolymers prepared by lowv temperature copolymerization of a'major proportion of an isoolefln having from four to seven carbon atoms with a minor proportion of an open-chain or linear conjugated dioleiin having from four to eight carbon atoms. The copolymer preferably contains irom 80 to 991/2 parts by weight of an isomonooleiin such as isobutylene or ethyl methyl ethylene copolymerized with from 1/2 to 20 parts by weight of a diolen such as isoprene;- butadiene-1,3.; piperylene; 2,3-dimethyl butadiene-1,3; 1,2-dimethyl butadiene-1,3; 1,3-dimethyl butadiene- This blend may be mixed with any conventional vulcanizing, accelerating, and

2 1,3; 1-ethy1 butadiene-1,3; 1,4-dimethy1 butadiene-1,3;`V the total monomeric material in the preferred mixture amounting to 100 parts by weight. The copolymerization may be effected by the usual-method of copolymerizing such monomers as disclosed in detail in U. S. Patents 2,356,128, 2,356,129, and 2,356,130 to Thomas and Sparks. Preferably a monomeric mixture containing irom to 99% by weight of an isomonoolen such as isobutylene and from 1 to 5% of a diolefln such as isoprene or butadiene-1,3 is used. These synthetic rubbers are known to the trade as GR-I, Butyl A, Butyl B,

Butyl C, and Flexon.

The neoprene blended with the Butyl rubber is a rubbery polymer of a 2-chlorobutadiene-l,3, commonly known as polychloroprene, or rubbery polymers of 2,3-dichlorobutadienel,3 or rubbery copolymers of a chlorobutadiene-1,3 with monomers copolymerizable therewith, such as isoprene, butadiene-1,3, styrene, acrylonitrile, etc. The typical neoprenes are known to the trade as Neoprene GN, Neoprene KN, .Neoprene I, "dR-M, and GR-M-lO. The rubbery homopolymer of chloroprene itself is preferred for the purpose of this invention. l

It is well known that it is diilicult to obtain satisfactory adhesion between isoolefin-diolefin copolymer synthetic rubber and other Americanmade or natural rubbers. however, with the edhesives of this invention, good adhesion is made possible between vulcanizable isoolen-diolen copolymer synthetic rubber and natural rubber or any of the sulfur-vulcanizable American-made rubbers, with no necessity of pre-vulcanizing one of the rubbers before adhesion. These rubbers can be adhered one to the other simply by placing one of the adhesive compositions of this invention between the unvulcanized rubber layers and then vulcanizing the composite structure by' the application of heat and pressure.

One embodiment of our invention is shown in the drawing in which:

Fig. 1 is a fragmentary view in section of a lining construction embodying this invention suitable for use in a pneumatic tire;

Fig. 2 is a fragmentary perspective view, broken away in section, of a pneumatic tire casing embodying the liner of Fig. 1 and, y

Fig. 3 is a fragmentary view in section of -another embodiment of our invention.

The preparation of typical adhesive composttions-within the scope of this invention is described in the following specific examples.

Example I The following ingredients were mixed thoroughly onaroll mili:

This composition was calendered 'into a solid. :flexible tie gum or strip. A strip of adhesive was then placed between a layer of a natural rubber composition and a layer of isoolen-diolefln copolymer synthetic rubber composition, both of which contained conventional compounding ingredients including sulfur and a vulcanizing agent and the composite structure vulcanized by the application of heat and pressure under conventional conditions. The resulting bond had a tensile strength of 18 pounds per linear inch.

Example II Parts by weight Isobutylene-isoprene copolymer (97.3) 50 Polychloroprene 50 Litharge Ferrie oxide 84 Magnesium oxide 2 Sulfur 1 Stearic arid l 1 Mercaptobenzothiazole 0.5 Tetra methyl thiuram disulfide 0.4 Dodecanoic acid 4 These ingredients were mixed on a roll mill and the resulting composition was dispersed in a mixture of toluene and ethyl acetate to form a cement. This cement was spread on the surfaces of a layer of isoolen-diolen copolymer synthetic rubber and a layer of butadiene-styrene copolymer synthetic rubber both of which contained conventional compounding ingredients including sulfur and accelerators, dried, and the coated surfaces were then placed together and vulcanized conventionally by heating at an elevated temperature and pressure. The bond had a tensile strength of pounds per linear inch.

The adhesive of this invention has been found to be of particular lvalue in the manufacture of the so-called tubeless tire in which the tire casing serves as the air container without the necessity for using an inner tube. Inasmuch as the rubbery material normally employed in a tire casing is either crude rubber or a4 rubbery butadiene-styrene copolymer through which air diiuses quite readily, it isY necessary to employ a barrier layer of material impervious to air to prevent loss of pressure. Butyl rubber has been found to be eminently satisfactory for this purpose except for the problem of adhering it to the rubbery material used in the remainder of the tire casing and it is this problem which can be met by the adhesive composition of the present invention.

As shown in Fig. 1 of the drawing, a composite liner II is constructed from a layer of Butyl between two layers I2 of the composition of Example I above. each approximately .004 inch.

thick. Layer I 2 of course contains ythe usual compounding ingredients including sulfur and an accelerator.

y The tire casing shown in Fig. 2 is then constructed in the usual manner employing liner II as the rst ply and using crude rubber as the rubbery material in the remainder of the carcass and tread I4. Liner II is turned back over bead I5 and bead cushions I6 of vulcanizable crude rubber composition are applied along the outer wall. The completed assembly is then vulcanized by heating under pressure in a mold in the usual manner.

, Another embodiment of my invention is shown in Fig. 3 in which a layer 20 of vulcanizable "ButyP rubber, containing the usual compounding ingredients is placed in face-to-face contact with a layer of cotton cord fabric 2| which has been previously coated or impregnated withl the cement 22 of Example II and dried. The fabric layer may then .be utilized as the inner fabric ply of a tire casing, serving to bond the Butyl rubber lining 20 to the crude rubber composition of the remainder of the tire carcass after vulcanization of the composite structure. The strength of the bond is approximately the same as the strength of the bond obtained in Example I above.

Similar results are obtained in using the adhesive composition of this invention for bonding rubber isoolefin-diolefin copolymers to other filamentary materials and to other sulfur-vulcanizable rubbery materials such as rubbery polymers of butadiene-1,3; isoprene; piperylene; 2,3-dimethyl butadiene-1,3; and the like; or robbery copolymers made by copolymerizing any of these materials with each other or with other copolymerizable ethylenic monomers such as styrene, acrylonitrile, methyl acrylate, methyl methacrylate. or the like.

The relative proportions of rubbery isoolendioletin copolymer and rubbery polychloroprene in the mixture may be varied over a. wide range. from about :20 to 20:80 by weight, but best results are obtained using approximately equal parts by weight, the preferred range of proportions being from 40:60 to 60:40 by weight. Pigmentation is not essential to obtain adhesive qualities, but iron oxide (either ferrous or ferric) in proportions from 20 to 100 parts by weight, for each parts by weight of the mixture of rubberyV materials does facilitate calendering and handling of the blend. Other pigments and vulcanizing agents, etc. may be added as desired. Tackifying resins in proportions from 1 to 10 parts by weight may be added to improve the tack of the tie gum compositions. Such resins may be hard cumar, rosin, pine tar, coal tar pitch, or the like. Cements made as herein disclosed may be further enhanced by the addition of hexa- 1riixizhylene diisocyanate or resorcinol formaldee. Y

These adhesives have made it possible to adhere an isoolen-diolefln copolymer synthetic rubber to either crude or American-made rubber without the necessity of prevulcanizing either of the rubbers, as was formerly the case. Further variations and modiiications may be effected within the spirit and scope of the invention as dened in the appended claims.

We claim:

1. A iiexible, vulcanizable, composite structure comprising a'layer of crude rubber; a layer com-f` prising a rubbery copolymer of fa major proportion of van isoolen having from 4 to`5 carbon* 4 to 8 carbonatoms, and from 20 to 80 'parts by weight of a rubbery polymer. oi a chlorohuta-l` diene-1.3.

2. A flexible. vulcaniaable. composite structure" comprising a layer of crude rubber; a.l layer comf' prising a robbery copolymer of a major propor` tion of an isooleiin having from 4 kto, 5 carbon atoms with a minor proportionof an open-chain conjugated dio'len'having from 4to o carbon atoms: and an interposed layer o! a solid, flexible adhesive in direct aflheringcontact with'each ofthe aforesaid layers comprising from 60 `=to 40 parts by weight of va' rubbery copolymer 'of a.l

major proportion of an isooleiln having from4 to 7y carbon` atoms with a minor proportion of an open-'chain conjugated diolefln having -from4`` to 8 carbon atoms,`f`andffrom 40 to'601parts by: weight of a rubbery' polymeroi a chlorobutafV diene-1,3.

'3. A] flexible, vulcanizable, composite structuref comprising val layer of a rubber, a layer of an isooleiin-diolen copolymer synthetic. rubber, andv an interposed layer of a'solid, 'flexible-adhesive composition yin direct adhering contact with each of the aforesaid layers comprising 50'parts by weight of a" copolymer of isobutylene'and isoprene, 50 parts by weight of polychloroprene, 42 parts 'by weight of iron oxide, and 1 part by weight of sulfur. 4. A flexible vulcanizable,

terposed layer of a lamentary material treated with an adhesive cement composition comprising from 80 to 20 parts by weight `of a copolymer of isobut-ylene and isoprene, to 80 partsv by weight of polychloroprene, 20 yto 100 parts byk weight of iron oxide, 'and 1A lto- 2 parts by-weig`ht of sulfur. said interposed layer being in direct adhering contact with each of the aforesaid layers.

5. A exible,

proportion of isoprene. and 'on either side of said body and in direct adheringcontact therewith a `layer comprising from 40 to '.60 'parts by weight of lpolychloroprene and from 60 to 40 parts byr weight of a copolymer of a ma'or proportion of isobutylene and a minor proportion of isoprene.

`6. A pneumatic tire having infcombinationfa carcass comprising a sulfur-vulcanized robbery material and an innerliner'ply, said inner liner ply comprising a rubbery copolymerof amajor proportion of an isoolen having Afrom 4 to 7 carbon atoms with. anopen-chain conjugated diolen having from 4 to 8 carbon atoms, anda bonding ply'interposed between and in direct adhering contact with said liner ply and said carcassl said bonding ply comprising,r a homogeneous mixture of 20 to 80 parts by weightofsaid rubbery copolymer with 80 to 20 parts by weight. of,y

composite structure comprising 'a layer of a rubber, a layer of 'a' oopolymer of va major proportion `of isobutylene with a vminor proportion of isoprene, and an inl vulcanizable inner liner for a tire comprisinga body of rublzzeryy copolymer of: fa major proportion ofisobutylene witha minor 'nomen to 403iparts a rubbery polymerof a chlorobutadieneil, said plies andfcarcass being bondedtogether by v ulcanization. 7. A method of adhering a rubberyfcopolymer of a major proportion of an isooleilril having `from 4 to' 7 carbonatoms with 'a minorproportion o! l an open-chain conjugated dioleiln f having from 4 to 8 carbon atoms to an unvulcanized rubber comprisinginterposing between and' indirect contact-with layersv ot said rubberylcopolymer and vsaidrubber a preformed. solid layer "of a vulcanizable adhesive composition which comprises substantially equal `parts of said ru'obery' copolymer and a polymer voi' a chlorobutadiene-Li; f and heating the composite product'to vulcanize the vulcanizable constituents. f`

` 8; A method of adhering an isoolen-dioleiln copolymer synthetic rubberto crude rubber comprising the steps of placing between and indirect contact with layers of said unvulcanized isooleilndioleiln ycopolymer synthetic rubber'and said unvulcanized crudeA rubberan interposed preformed,

solid layer of a vulcanizable adhesive composition which comprises substantially equal parts of a copolymer of isobutylene and isoprene anda polyf mer of chlorobutadienel; and heating the 4coin'- lpositeiproduct to :vulcanize the vulcanizable con'- stituents. i ,Y

9. @A1-method of adhering an isooletln-dioleiln copolymer syntheticrubber to crude rubber comf vprising the steps of placing betweenand in direct contact ywithvlayers of. said -unyulcanizedV isoolen-diolen .copolymer syntheticv rubber and unvulcanized crude yrubber `an. interposed preformed, solid layer of an `adhesive composition comprising from 40-60 parts by weight of a copolymer ofrisobutyleneand isoprene, and from 40-60parts by weight of. polychloroprene,"and

lsubjecting thecomposite structure tofheat and pressure to vulcanize the assembly.`

g 10. A pneumatic .tire havingin combination carcass comprising i a sulfur-vulcanized rubbery .material and an inner linerply, said inner rliner ply comprising a `layer of a rubbery copolymer of an isoolen having from'4to7 carbon atoms with an `open-,chain conjugated dioletln having `from 4 to 8 carbon-atomsin face-to-.face contact with alayer of cord fabric impregnated with a v`homogeneous -Kmixturer of 20;,to 80 .parts by weight of ysaidjrubbery copolymer with 80 to 2O .j

'parts by weight of a vrubbery polymer :of a chlorobutadiene-1,3, said i ner ply and carcass all being integrally bonded together.

`-1l. ,A pneumatictire having incombination a vcarcass, .comprising a sulfur-vulcanized, rubbery f `material, bead members, and outer bead cushion vmembers comprisingv afsulfur-vulcanized rubbery material, and an inner, lineLmSmbenin direct adhesive contact with the inner face of said carcass extending around said-bead members be vtween said bead members and, said bead cushion members, saidy liner member Acomprising a .core

member disposed between a pair of bonding layers in co'exten's'ive direct contact therewith, said core kmember kconstituting a continuous vstratum comprising a rubbery copolymer' of a majorproportion of an isoolenhaving fromf4 to 7y carbon atoms with afminor proportionof` an open-chain conjugated diolefin having from 4to `8 carbon atoms, said bonding layers comprising from ,40

to fparts"by`weight of saidfoopolymer and of rubbery polychloroprene'. .DONALD v- SARBACH f *y i GEORGE nLooMijs.

i (References on followingr page.)

REFERENCES cru-:D Number Name Data 2.354.426 Briant July 2.5. 1944 myx; lllsognrtfcrens are 0f record n the 2,405,943 Deering ec al. Aug. 2o, 1946 2.442.083 Hall et al. May 25. 1948 UNITED STATES PA'I'EN'IS 5 2.443.679 Garvey June 22, 1948 Number Name v Date 2.467.322 Lightbown et al. Apr. 12. 1949 1,171,449 Mcoienan Feb. 15, 1916 2.469.710 Baldwin May 10. 1949 Thomas De 26, 1939 2.471.905 Smith May 31. 1949 

1. A FLEXIBLE, VULCANIZABLE, COMPOSITE STRUCTURE COMPRISING A LAYER OF CRUDE RUBBER; A LAYER COMPRISING A RUBBERY COPOLYMER OF A MAJOR PROPORTION OF AN ISOOLEFIN HAVING FROM 4 TO 5 CARBON ATOMS WITH A MINOR PROPORTIONS OF AN OPEN-CHAIN CONJUGATED DIOLEFIN HAVING FROM 4 TO 6 CARBON ATOMS; AND AN INTERPOSED LAYER OF A SOLID, FLEXIBLE ADHESIVE IN DIRECT ADHERING CONTACT WITH EACH OF THE AFORESAID LAYERS COMPRISING FROM 80 TO 20 PARTS BY WEIGHT OF A RUBBERY COPOLYMER OF A MAJOR PROPORTION OF AN ISOOLEFIN HAVING FROM 4 TO 7 CARBON ATOMS WITH A MINOR PROPORTION OF AN OPEN-CHAIN CONJUGATED DIOLEFIN HAVING FROM 4 TO 8 CARBON ATOMS, AND FROM 20 TO 80 PARTS BY WEIGHT OF A RUBBERY POLYMER OF A CHLOROBUTADIENE-1,3.
 7. A METHOD OF ADHERING A RUBBERY COPOLYMER OF A MAJOR PROPORTION OF AN ISOOLFEIN HAVING FROM 4 TO 7 CARBON ATOMS WITH A MINOR PROPORTION OF AN OPEN-CHAIN CONJUATED DIOLFIN HAVING FROM 4 TO 8 CARBON ATOMS TO AN UNVULCANIZED RUBBER COMPRISING INTERPOSING BETWEEN AND IN DIRECT CONTACT WITH LAYERS OF SAID RUBBERY COPOLYMER AND SAID RUBBER A PREFORMED, SOLID LAYER OF A VULCANIZABLE ADHESIVE COMPOSITION WHICH COMPRISES SUBSTANTIALLY EQUAL PARTS OF SAID RUBBERY COPOLYMER AND A POLYMER OF A CHLOROBUTADIENE-1,3; AND HEATING THE COMPOSITE PRODUCT TO VULCANIZE THE VULCANIZABLE CONSTITUENTS. 